1. Field of the Invention
The present invention relates to switch actuating units and, more particularly, to switch actuating units having electrical or electromechanical limit position switches actuatable by a mechanical sensing device.
2. Description of the Related Art
Switch actuating units are well known in the art. For example German Patent No. DE-AS 2511603 describes a switch actuating unit for a driven shaft, especially a threaded spindle. This unit has limit switches located at opposite ends of the threaded spindle. The threaded spindle has a threaded actuating element mounted thereon which runs along the spindle as the spindle rotates. The direction of movement is towards one or the other of the limit switches and is dependent on the direction of the rotation of the spindle. When the actuating element reaches one of the limit switches at an end position, the switch is actuated and the drive for the threaded spindle is shut off.
A disadvantage of this device is due to the mounting position of the limit switches. Because the switches are at either end of the spindle, the actuating element moves independently of the switches and it is necessary to wire the switches accordingly. If the end position of the actuating elements are to be retrofitted, wiring the switches on moving parts of the system, as would be necessary here, poses mounting problems and creates a risk that the wires could be damaged by the moving parts. For the embodiment described by this German patent secure mounting of the switches is only possible at the end positions of the spindle and thus, the disadvantages mentioned above are inherent to this device.
It is thus desirable to produce a switch actuating unit which can be easily retrofitted. Production of such a unit in which the switches move together with the actuating element is also desirable. This device should also eliminate the possibility of damaging any wiring during mounting, retrofitting and operation.